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Dumbbell Jackknife Sit-Up
A weighted core exercise that targets the rectus abdominis and hip flexors to build strength and stability; commonly scaled by bending the knees or reducing weight.
About Exercise
Equipment
Dumbbells
Difficulty
4/5 • Intermediate
Primary Muscle Groups
Abs, Hip Flexors
Secondary Muscles
Shoulders, Quads
Popularity Score
6
Goals
Training Style
Setup Requirements
Requires Rack
No
Requires Bench
No
Requires Spotter
No
Space Needed
Medium
Noise Level
Low
Muscle Breakdown
View Muscle MapAbs
10/10Rectus Abdominis, Transverse Abdominis
Hip Flexors
8/10Iliopsoas
Obliques
6/10External Obliques
Shoulders
4/10Anterior Delts
Quads
4/10Rectus Femoris
Programming
Typical Rep Range
8-15 reps
Rest Between Sets
45-90 seconds • Allow core to recover to maintain form.
How to Perform
Lie flat on your back holding a single dumbbell with both hands, arms extended overhead and legs straight out.
- Brace your core and press your lower back into the floor.
- Simultaneously lift your legs and upper body, bringing the dumbbell toward your shins.
- Balance on your glutes at the top of the movement, forming a V shape.
- Lower your torso and legs back to the starting position with control.
- Keep your heels and the dumbbell hovering just off the floor between reps.
Coaching Tips
Form Cues
- Ribs down
- Squeeze abs
- Control the descent
- Keep arms straight
Breathing
Exhale forcefully as you lift into the V-up; inhale as you lower back down.
Tempo
2-1-1
Range of Motion
From a fully extended hollow body position to a V-shape where the dumbbell meets the lower legs.
Safety
Safety Notes
- Ensure a secure grip on the dumbbell.
- Stop if you feel sharp pain in the lower back.
- Start with a light weight to master timing.
Spotting
Not recommended; drop the weight safely if muscle failure occurs.
Common Mistakes
- Using momentum to swing up
- Arching the lower back
- Bending knees excessively
- Rushing the eccentric phase
When to Avoid
- Acute lower back pain
- Shoulder impingement
- Diastasis recti
Flexibility Needed
- Hamstring flexibility
- Shoulder flexion
Build Up First
- Bodyweight V-Up competency
- Hollow body hold mastery
Also known as
Weighted V-Up, Dumbbell V-Up, Weighted Jackknife
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